A 150-kDa glycoprotein isolated from Solanum nigrum L. has cytotoxic and apoptotic effects by inhibiting the effects of protein kinase C alpha, nuclear factor-kappa B and inducible nitric oxide in HCT-116 cells

This study was carried out to investigate the anticancer effects of a 150-kDa glycoprotein isolated from Solanum nigrum L. (SNL glycoprotein) on spontaneously and experimentally induced tumor promotion in HCT-116 cells. For spontaneously induced tumor promotion, we evaluated the cytotoxic and apoptotic effects in HCT-116 cells using 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT), DNA fragmentation, and H33342 and ethidium bromide staining assays. SNL glycoprotein had remarkable, dose-dependent cytotoxic and apoptosis-inducing effects at low concentrations. For experimentally induced tumor promotion, we investigated whether the SNL glycoprotein was able to regulate the activity of protein kinase C alpha (PKCα), the DNA binding activation of nuclear factor-kappa B (NF-κB), the activity of NF-κB protein, and the production of nitric oxide (NO) in HCT-116 cells stimulated with 12-O-tetradecanoylphorbol 13-acetate (TPA) using electrophoretic mobility shift assays (EMSA), Western blot analysis, and NO assays. As expected, SNL glycoprotein dose-dependently inhibited PKCα translocation, NF-κB DNA binding activity, NF-κB protein activity and NO production in HCT-116 cells stimulated with TPA (61.68 ng/ml, 100 nM). Collectively, these results suggest that SNL glycoprotein can induce apoptosis through the modulation of signal mediators. Therefore, we speculate that it could be used as a chemotherapy agent even at low concentrations in HCT-116 cells.